Modern cellular communication systems, such as third generation partnership project (3GPP), 3GPP long term evolution (3GPP LTE) and 3GPP LTE-advanced (3GPP LTE-A) are in large part directed to the use of full duplex communication, because many devices supported by such networks impose significant demands on the available frequencies. However, increasing numbers of devices are designed for and deployed in uses in which half duplex frequency division duplex (FDD) can be used, and can be advantageous because half duplex FDD can be achieved a lower cost than can full duplex FDD. One application in particular that can be supported by half duplex FDD is machine type communications (MTC) because MTC devices often engage in infrequent, short duration communication that can be easily accommodated by half duplex FDD. In 3GPP LTE, half duplex operation is a supported mode, but not mandatory, so that numerous eNodeBs (eNBs) may exist into which half-duplex FDD has not been implemented, and the use of half-duplex devices in systems designed to support only full-duplex can add significant implementation complexity.
For a half-duplex FDD device, the device may continuously listen to the downlink channels except when instructed by the network to transmit on the uplink. Uplink transmissions may be based on higher-layer configuration, for example, Channel Quality Information, in response to downlink transmission, for example, acknowledgements or ACK/NACK, or scheduled, for example, data transmission. In this case, the scheduler must ensure that there are no scheduling conflicts for half-duplex FDD devices. Ensuring that there are no scheduling conflicts will require the scheduler to consider data and control traffic in both directions when making scheduling decisions. For example, the downlink scheduler must know of current uplink transmission. Likewise, the uplink scheduler must be aware of upcoming downlink ACK/NACK or semi-persistently scheduled transmission. Such operations significantly add to scheduler complexity. In addition, for a full-duplex FDD device, such scheduling restrictions are not needed, and this difference between half-duplex and full-duplex devices can make concurrent support more complicated.